Constitutive modelling of abdominal organs

Abdominal organs are very susceptible to trauma. In order to protect them properly against car crash and other impact consequences, we need to be able to simulate the abdominal organ deformation. Such simulation should account for proper stress-strain relation as well as stress dependence on strain rate. As the step in this direction, this paper presents three-dimensional, non-linear, viscoelastic constitutive models for liver and kidney tissue. The models have been constructed basing on in vivo experiments conducted in Highway Safety Research Institute and the Medical Centre of The University of Michigan (Melvin et al., 1973). The proposed models are valid for compressive nominal strains up to 35% and fast (impact) strain rates between 0.2 and 22.5 s(-1). Similar models can find applications in computer and robot assisted surgery, e.g. the realistic simulation of surgical procedures (including virtual reality) and non-rigid registration.

Factors influencing outcome after blunt duodenal injury

Thirty-six patients with blunt duodenal injury have been treated at Detroit General Hospital since 1960. The majority of the patients were driving an automobile under the influence of alcohol and none were wearing seat restraints. Diagnosis was often delayed due to a failure to recognize the significant, but subtle, physical and roentgenographic findings of retro-peritoneal injury. Morbidity and mortality were related to a delay in operative intervention, the severity of duodenal injury, the presence and degree of associated pancreatic injury, and the choice of operative therapy. Patients with intramural hematoma or complete duodenal perforation without pancreatic injury did well with simple closure or evacuation of the hematoma. Patients with duodenal perforation and minor pancreatic injury did best after primary closure and pancreatic drainage if operation was performed within 24 hours; delay beyond 24 hours resulted in a high incidence of duodenal fistula after simple closure, and therefore is an indication for a bypass procedure, such as a distal gastrectomy, vagotomy, tube duodenostomy, and gastrojejunostomy. Patients with combined duodenal and major pancreatic disruption did best after a bypass procedure when the main pancreatic ductal system was intact, whereas pancreaticoduodenectomy was the best procedure when the main pancreatic duct was disrupted.

Management of venous injuries

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Suicides by sharp force: typical and atypical features

A total of 65 consecutive cases of suicide by sharp force were investigated by evaluating the autopsy and prosecution department records. Suicides constituted 17% of all fatalities from sharp force autopsied between 1967 and 1996. Young males and persons with a psychiatric history predominated among the persons who chose this "hard" method of suicide. The most common implements used were knives (62%) and razor blades (15%). Cutting injuries in isolation were present in 26, stab injuries in isolation in 24 and a combination of both in 15 fatalities. The number of injuries per case varied from 1 to 37 but 1/3 showed one injury. More than 85% of the cutting injuries were located at the wrist, elbow crease or neck whereas 79% of the stab injuries involved the ventral aspect of the trunk. Perforation of clothing was present in 16 (52%) out of 31 stab injuries to the trunk. Injuries to more than one body region were observed in 34 (52%) cases. Tentative marks were present in 50 (77%) fatalities and the number varied from 1 to 60 per case. Superficial incisions of the fingers were found in 15% with razor blades constituting the weapon in half of these cases. Deviations from these typical patterns occurred not infrequently. The utter determination of the victim to carry it through or the use of unusual weapons resulted in a few bizarre cases which are outlined briefly.

Post-traumatic adrenal apoplexy

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Jaundice and wound healing: an experimental study

Obstructive jaundice was induced in rats by ligation and division of the common bile duct. The healing of a standard gastric incision and a parietal peritoneal defect in these animals showed histological evidence of delayed healing compared with controls. The bursting strength of the abdominal incision was also lowered, but not that of the stomach, probably because of the adhesions which reinforced the gastric incisions. Angiography did, however, reveal delay in angiogenesis in the gastric wounds of jaundiced animals. The possible causes of this delay in healing and its clinical implications require further investigations.

Partial left heart bypass for thoracic aorta repair. Survival without paraplegia

OBJECTIVE

Emergency repair of the torn descending thoracic aorta has been associated with an almost 15% incidence of paraplegia. The literature to date suggests that the incidence of paraplegia is not influenced by mechanical adjuncts to enhance distal aortic perfusion during cross-clamping and therefore, "clamp and sew" has been considered an acceptable technique. The purpose of the present study was to review our experience with repair of descending thoracic aortas using partial left heart bypass and to compare this favorable initial experience with the available data on the use of the heparinless centrifugal pump.

DESIGN

A retrospective review of the routine use of partial left heart bypass in 16 consecutive patients with descending thoracic aorta disruptions. Results were compared with similar reports in the recent literature on trauma.

SETTING

A level 1 trauma facility in the Denver, Colo, metropolitan area.

PATIENTS

All patients with multisystem blunt trauma with a mean injury severity score of 36.

INTERVENTION

Repair of the descending thoracic aorta disruption using partial left heart bypass with a heparinless centrifugal pump.

MAIN OUTCOME MEASURES

Primary outcome measures were survival and paraplegia; other monitored variables included proximal and distal aortic pressure, flow rates, and oxygen transport.

RESULTS

Among the 14 survivors (88%) there were no cases of paraplegia, and intraoperative hemodynamics and oxygen transport were well maintained with partial left heart bypass. This experience is added to the available reported data on the use of the centrifugal pump. In these additional 42 patients, the mortality rate was 7%, with no incidence of paraplegia.

CONCLUSIONS

This collective experience failed to disclose a single case of paraplegia when partial left heart bypass was employed for repair of descending thoracic aorta. Moreover, the use of partial left heart bypass in this cohort of critically injured patients is associated with survival and perioperative morbidity rates comparable with the best recent reports of emergency thoracic aortic repair.